Various types of voltage blocks are known. There are, for example, the devices and systems described in the following U.S. Pat. Nos. 6,423,143; 6,021,965; 5,944,045; RE35,883; 5,787,928; 5,759,277; 5,746,831; 5,737,174; 5,727,931; 5,725,150; 5,707,013; 5,655,896; 5,632,816; 5,549,755; 5,538,186; 5,526,986; 5,518,186; 5,341,990; 5,340,289; 5,326,031; 5,288,029; 5,271,569; 5,255,856; 5,221,194; 5,208,078; 5,197,676; 5,193,750; 5,096,126; 5,094,389; 5,078,168; 5,033,942; 4,982,903; 4,932,589; 4,921,169; 4,884,752; 4,879,137; 4,878,622; 4,792,092; 4,771,729; 4,383,644; 4,313,475; 4,275,834; 4,085,892; 4,020,866; 4,017,029; 3,937,400; and, 3,933,285; as well as WO 2005/014178; GB2,166,982; JP4-267961; JP4-200662; JP7-88407; JP51-54638; JP54-101843; JP4-66149; JP3-178354; JP3217394 and, JP3378058. U.S. Pat. No. 4,337,282 is also of interest. The disclosures of these references are hereby incorporated herein by reference. This listing is not intended to be a representation that a complete search of all relevant art has been made, or that no more pertinent art than that listed exists, or that the listed art is material to patentability. Nor should any such representation be inferred.